IgE Immunology

Question 1

Type I hypersensitivity

Answer 1

Allergic responses mediated by IgE

Question 2

Type II hypersensitivity

Answer 2

Antibody directed against tissue antigens- mediated by IgG

Question 3

Type III hypersensitivity

Answer 3

Immune Complex mediated disease- mediated by antigen+IgG

Question 4

Type IV hypersensitivity

Answer 4

delayed hypersensitivity mediated by T cells

Question 5

Atopy

Answer 5

Atopy – genetic predisposition to develop IgE antibodies upon exposure to environmental allergens
• ALMOST ANY PROTEIN CAN INDUCE AN ALLERGIC RESPONSE IN AN ATOPIC INDIVIDUAL

Question 6

Allergy

Answer 6

A disease induced by reaction to a usually innocuous antigen

Question 7

IgE

Answer 7

standard Ig structure, heavily glycosylated and has binding sites for Fc(epsilon)R. Normally very low concentration in serum, usually cell bound found at host-environment interfaces. Binding sites for Fc(epsilon)R on mast cells and basophils

Question 8

3 manifestations of allergic reactions

Answer 8

anaphylactic shock, allergic rhinitis, and chronic bronchial asthma

Question 9

Both mast cells and basophils

Answer 9

Both express HIGH affinity FcεR
Both contain histamine, TNF-α and leukotrienes in cytoplasm
Degranulation releases the mediators

Question 10

Mast cells

Answer 10

Mast cells - tissue bound, compartmentalized as mucosal or connetive tissue, contain potent vasoactive compounds and cytokines

Question 11

Types of Mast cells

Answer 11

MC-tryptase (prominent within the mucosa of the respiratory and gastrointestinal tracts) and MC- tryptase and chymase (localized within connective tissue, such as the dermis, submucosa of the GI, heart, conjunctivae, and perivascular tissues)

Question 12

common component of allergens

Answer 12

Chitin- a polysaccharide not found in mammals. This induces expression of chitinase- a possible inducer of allergenic antigen generation and release of vasoactive mediators

Question 13

type of proteins that commonly become allergenic

Answer 13

Almost anything can be an allergen but there is a trend towards proteins with enzymatic activity or ones that induce it
Timing is important: decreased early exposure to infections in the genetically predisposed individual is associated with insufficient T regulator control of IgE (more later)
route - mucosal exposures predominate

Question 14

First step of an allergic rxn

Answer 14

allergen taken up and presented by DCs, Th2 response activates (IL-4) B-cells which produce mostly IgE antibodies. IgE Abs bind mast cells and cause degranulation

Question 15

Fc(epsilon)R

Answer 15

the only FcR that can be activated/bound by Ig not bound to antigen

Question 16

Early response

Answer 16

WITHIN 15 MINUTES
PROSTAGLANDINS & LEUKOTRIENE RELEASE
DIRECT COMPLEMENT ACTIVATION
CANNOT HAPPEN IF NO PREVIOUS EXPOSURE

Question 17

Late response

Answer 17

COMPLETELY DEPENDENT ON Th2 ACTIVATION
AND CYTOKINES IL3,4,5,13,AND 10
EOTAXIN
CHARACTERIZED BY EOSINOPHILS

Question 18

clinical manifestations of an allergic response depend on

Answer 18

the location/site of reaction

Question 19

Anaphylaxis

Answer 19

systemic, entry via stings, ingestion or inhalation(rare), typical allergens are insect venom, drugs, foods. Main symptoms are shock, hypotension, wheezing, urticaria and angioedema

Question 20

eczema (atopic dermatitis), urticaria, angioedema

Answer 20

mostly skin, usually do to contact ingestion or inhalation(rare). Causes are uncertain, food, and drugs. Main symptoms are pruritic, vesicular, swollen lesions

Question 21

Allergic rhinitis, conjunctivitis

Answer 21

mainly affects nose and eyes. due to contact with mucous membrane. Allergens include pollens, dust mines, animal dander and molds. Causes runny nose, redness and itchy eyes.

Question 22

Asthma

Answer 22

affects the lungs, caused by inhalation of pollens, dust mites, animal dander, and molds. Causes wheezing, dyspnea, tachypnea.

Question 23

Allergic gastroenteropathy

Answer 23

affects the GI tract due to ingestion of various foods leads to pain, bloating, vomiting and diarrhea.

Question 24

Hygiene hypothesis

Answer 24

Decreased childhood infection and later exposure
Early exposure to infections less allergy
Large families, rural residence and daycare associated with less allergy
Lack of early exposure associated with deficiency of Tregs that control IgE synethesis

Question 25

Detection of Allergies

Answer 25

careful medical hx*, Skin testing(more sensitive than blood test), RAST, In vitro assays

Question 26

RAST (radio allergo sorben test)

Answer 26

pt. serum is added to a disc with allergen, IgE in serum binds the allergen, after washing a radio-labled anti-IgE is added

Question 27

Treatment options

Answer 27

1. avoid the allergen
2. immunotherapy-allergy shots or sublingual (SILT)
3. block/suppress the immunologic response with monoclonal anti-IgE
4. possible vaccination in future

Question 28

How does decreased early exposure to infections affect allergies

Answer 28

Timing is important: decreased early exposure to infections in the genetically predisposed individual is associated with insufficient T regulator control of IgE (more later)
route - mucosal exposures predominate

Question 29

IL-5 is released by _______ and does _______

Answer 29

mast cells and Th2 cells; recruits eosinophils

Question 30

3 major cell types that mediate allergy

Answer 30

basophil, mast cell, and eosinophil

Question 31

leukotrienes functions

Answer 31

increase vascular permeability
inflammation
bronchioconstriction